Choose the topic:

• First hip replacement
• Types of hip replacement implants
• Most commonly used hip implants
• Hip implants manufacturers

Hip replacement is a medical procedure  during which the diseased hip joint is replaced with an artificial implant so that the function of the hip would be retained. Usually, the term Hip replacement means total hip arthroplasty, a replacement of the whole hip joint, whereas hemiarthroplasty is a replacement of only one articulation surface of the joint, while the other remains unchanged.

First hip replacement
First attempts to replace a hip joint were carried out with implants made of ivory in the late 19th – early 20th century. In the next few decades a large number of completely artificial implants, varying in comprising materials, design, application were introduced which gradually led to an increasing overall improvement of hip replacement outcomes and patients’ quality of life. Today it is one of the most common and routine orthopedic procedures.

Types of hip replacement implants
The variety of different hip implant types makes it quite clear that none of them is yet perfect. And what would be a perfect hip implant? The answer is both simple and complex – it would mimic the natural structures of the joint and surrounding bones as much as possible, in terms of stability, durability, elasticity and low deterioration. Unlike artificial materials, from which implants are made, bone is an ever changing tissue, renewing its structure and readjusting to forces acting on it. In this way bone sustains its qualities throughout the most part of a lifetime.

Furthermore, articular surfaces of the joint are covered with cartilages and lubricated with synovial fluid so as to reduce friction, to absorb some of the impact force and to allow normal and fluent movements. This makes repetition of the joint function a hard task. Firstly, implants should withstand very high forces, be resistant to impact-caused micro-changes in the structure, get along well with surrounding tissues and provide a wear-and-tear resistant articular interface.

The design and biomechanics of modern day implants have not changed much since the beginning of hip replacement treatment. What really changed was the material used. Implants consist of two main parts – acetabular cup which acts as an artificial hip socket, or acetabulum, and femoral component, replacing the femoral head and neck. Acetabular cup and femoral component are commonly anchored into bone using bone cement mass which hardens almost immediately after application and forms a strong bond with the bone. Some newer implants today have a porous coating that mimics bone trabeculae. Additional fixation is then formed, as native bone grows into this coating.

Most commonly used hip implants
Here are some examples of most commonly used hip implants:

Metal ball and plastic cup liner implants:
This type of implants has been used since the early 1960s. Now with improved, so-called “highly crosslinked” polyethylene plastic liners, a much lower wear of the implant is achieved.

Ceramic ball and plastic cup liner implants:
Ceramic heads of femoral components are harder and more scratch resistant than ones made of metal. Together with plastic cup liners they offer greater wear resistance compared to implants with metal heads.

Metal-on-metal implants:
Metal-on-metal implants have no liners and the heads are bigger which has a benefit of increased motion range and a lower incidence of hip dislocation. Furthermore, metal-on-metal implants offer greater wear resistance compared to plastic components and cause less inflammatory reactions. However, there is an ongoing discussion, that metal wear debris, generated from metal-on-metal implants, may be associated with increased metal ion concentrations in the blood. Whether this actually affects the health of a patient is not yet known.

Ceramic ball and ceramic liner
This type of implants is considered to be one of the most reliable. With their longevity and durability fully ceramic implants are especially suitable for younger, more active patients. Since ceramics is the hardest material used in implants, it has an extremely low wear rate, measured about 0,0001 mm per year. Ceramic surfaces are also the smoothest which has an effect on wear rates as well. However, long-term data on their reliability is still limited, as this type of implants is relatively new.

Hip surface replacement (hip resurfacing)
Hip resurfacing is an alternative to total hip replacement, when the proximal femoral bone is conserved and only the head of femur is “resurfaced” – a hollow metal cap is placed over it. Hip socket is replaced just as it would be in total hip replacement. Hip resurfacing offers lower risk of hip dislocation and relatively fast recovery after the procedure. Since much less bone is removed, any further revision surgeries of hip joint are made easier. But this procedure should only be performed in patients with adequate bone mass and low risk of femoral neck fracture.

Hip implants manufacturers
Notable hip implants manufacturers are: Biomet, Inc., DePuy Orthopaedics, Stryker Orthopaedics, djo surgical, Wright Medical Technology, Inc, Zimmer Orthopaedics and others. Usually, all of them produce several types of implants. Such variety can be confusing but it is also useful as every patient is unique, has his own pace of life, health condition, activities and movement capacities, so an implant must be chosen individually. Well selected implant will last longer and serve better.

We offer you a variety of hip implants. Each individual case is carefully evaluated in order to select the implant that suits one's needs the best.

Knee replacement implants abroad in Cyprus
Choose the topic:
• Knee implants trends
• Total knee replacement vs partial
• Fixed vs Mobile bearing implants
• Cruciate-retaining knee implants
• Success of knee replacement

Knee replacement implants then and now
First knee replacement implants were designed in the late 1950s in order to change damaged cartilage and bone of the knee. The knee replacement surgery quickly became one of the greatest examples of innovative surgery and has resulted in significant increase in the quality of life for people with damaged knees. As a result, the number of replacements has been growing dramatically every year.

The increasing need to upgrade the results of surgical outcomes has led to improvements in knowledge and understanding of knee function, more advanced surgical techniques and implant designs. Over the past years the number of implants available for the patients has significantly increased. Geometrical, anatomical, structural and functional solutions of latest knee implants impressively simulate natural knee joint allowing the knee implant to accomplish function of healthy knee joint such as flexing and rotating during the activities of daily life. There are multiple types of knee implants that doctors and patients can discuss before choosing the best option. Some of implants are mechanical which work as a simple joint and some of them are even computerized which have microprocessors and integrated fluid systems.

Total knee replacement vs partial knee replacement
Total knee replacement and partial knee replacement are the main types of knees replacement surgery. Both surgeries show highly successful results. The difference is whether the entire knee joint needs replacement or only a part.

In a total replacement knee joint ant other biological materials that have been damaged by disease or etiological factors are replaced with foreign synthetic or organic materials.

Indications for partial knee replacement surgery are the same as for total knee replacement: to relieve pain and eliminate dysfunction of the knee, but for partial surgery disease should be isolated, ligaments need not to be damaged, and any deformity or lesion should be correctable.

In total knee replacement, the implants are used to resurface the ends of the femur and tibia. If only one side of the knee joint is damaged, partial knee replacement is applicable and smaller implants can be used to resurface only the damaged side.

Fixed bearing vs Mobile bearing implants
Currently mostly used types of implants are fixed bearing and mobile bearing implants. It is known that both prostheses designs show very good survival rates around 95% in 10 years. Fixed bearing prostheses are most popular and accessible implants. A fixed bearing prosthesis includes a femoral detail having a medial and lateral condyle superficies and different tibial pallets allowing for maximum flexion of 110 degree at the knee joint. Usually it is made of strong materials such as titanium or cobalt chrome alloy. This design is the best choice for patients who do not have extra weight and who are not very active in sport or for elder people.

Mobile bearing implants are more suitable to younger and more active patients. Mobile implant provides patients with more impressive flexibility on the medial and lateral sides of the knee. Also because of the reduced wear of polyethylene and bone-prosthesis interface and more normal kinematics loosening after surgery is minimal.

Cruciate-retaining knee implants
Another type of implants retain or substitute posterior cruciate ligament. They are mostly recommended for patients with extremely damaged knees or elusive ligaments of the knee. Cruciate-retaining knee prosthetics are designed to support the knee joint by remaining the posterior cruciate ligament. Posterior-stabilized implants intend to change the posterior cruciate ligament by a polyethylene patch and femoral cam.  Both implants prevent anterior rotation of the femur on the tibia and create stability. Potential advantages of these designs in comparison with fixed and mobile bearing models include less technically complicated procedure and more stable component interface and increased flexibility.

What determines success of knee replacement?
Success of surgery depends on correct selection of patients and proper implants for joint replacement. The choice of prosthesis depends on individual patient properties including age, weight, level of activity, health, cost of prosthesis, surgeon choice and experience of the surgeon. The most important components of knee implants are femoral component, tibial component and patellar component. All components of implant must be strong, flexible and resistant and should be designed of durable materials such as steel, cobalt, titanium, cement, ceramic or synthetic materials such as polyethylene which have to promote smooth movement and minimal future deterioration.

After knee replacement surgery positive achievements in pain and function management are quickly observed as well as quality of life and increased mobility. It may decrease social isolation and have other benefits, such as improved sport activity. Unfortunately, sometimes choosing wrong implant for wrong patient can lead to failure of knee replacement. Better understanding of the kinematics of the knee and changes in design can lead to better outcomes for patients.